S->o 



Journal of Applied Microscopy. 



Zimmermann regards as a normal process during certain nuclear divisions. 

 Humphrey, however, considered Zimmermann 's sickle stage as an artificial pro- 

 duction, and this seems also to be Strasburger's view. 



While experimenting on the action of various killing fluids, the writer made 

 up the following mixture, which was tried on some root-tips of the common 



onion : 



Absolute Alcohol, 95 cc. 



Chloroform, 5 cc. 



Glacial Acetic Acid, 1 cc. 



Chromic Acid (1 per cent, aqueous solution), . 1 cc. 



This fluid had an exceedingly violent action on all cell structures. The cells 

 were badly shrunken, the nuclei displaced, and the cytoplasm more or less dis- 

 torted.* Nearly all the nuclei in the cells of the peripheral layers showed the 

 sickle stage. In the central cells there was little displacement, although the 

 cells were much shrunken. This was probably because the killing fluid, pene- 

 trating from opposite sides, met here, and thus had an equalizing effect. These 

 nuclei were nearly all in the resting stage, as will appear from an examination of 

 the figures. The nuclei were nearly all crowded toward the peripheral walls of 

 the ceUs, while the nucleoli were generally pushed in the opposite direction 

 toward the inner sides of the nuclei. No such displacement of nuclei is to be 

 seen in well-killed sections. In figures 5, G, and 8 are shown nucleoli in various 

 stages of distortion. Hgure 5 shows the nucleolus merely crowded against the 

 nuclear membrane, while in figures 6 and H it is considerably flattened. In fig_ 

 ure 7 th^e dark, sickle-shaped layer on the inner side of the nucleus is probably 

 due to a distortion of the nucleolus with some chromatin deposited on this. 

 Although the chromatin was usually in the resting condition, it was brought into 

 a partial synapsis stage by the violent action of the fluid. Figures 1 and 2 give 

 the general appearance where the dark layer of material is apparently produced 

 by a contraction of the chromatin on the inner side. In figures 3 and 4 the 

 sickle-shaped body is caused by a distorted nucleolus around which is a layer of 

 chromatin. 



The writer has studied the cells of the onion root-tip for years, but has never 



observed the sickle stage in them before. If such characteristic figures can be 



produced in resting nuclei in wholesale quantities, it does not seem that much 



importance should be attached either to the sickle stage of the nucleolus or to the 



one-sided contractions of the chromatin which appear in the prophases of karyo- 



kinesis, when the chromatin band is orienting itself freely inside of the nuclear 



membrane, and when the nucleoli are lying free in the achromatin of the nuclear 



cavity. 



John H. Schaffner. 



Botanical Laboratory, Ohio State University. 



The Use of Acetone in Histology. 



Preliminary Aok. — Acetone, although not officially recognized by the United 

 States Pharmacopiiiia, is, nevertheless, used to a greater or less extent in ther- 

 apeutics and for technical purposes. 



